Gas sampling device

ABSTRACT

A gas sampling device having a sampling head with supply and take-up reels mounted on opposite sides of the head to accommodate a filter material in tape form. The sampling head has two blocks which are yieldably urged toward each other to clamp a portion of the filter tape between the blocks. Each block is formed with a gas chamber which is positioned so that a sample of gas can be passed through the filter tape between the blocks. A spool with cam surfaces having serrated teeth is connected to one of the blocks and positioned so that when the spool is rotated the cam surfaces momentarily shift one of the blocks away from the other block and advance the filter tape through the head. The supply reel is connected to a drag clutch and the take-up reel is driven through a friction clutch so that the tape is always under a slight tension.

United States Patent Keefer et al.

15] 3,654,801 [451 Apr. 11, 1972 [54] GAS SAMPLING DEVICE [72]Inventors: Richard D. Keefer; John S. Wyman, Jr.,

both of Ann Arbor, Mich.

[73] Assignee: The Bendix Corporation [22] Filed: Feb. 14, 1969 [21]Appl. No.: 799,367

[52] US. Cl ..73/28 [51] Int. Cl. ..G01n 21/28 [58] Field ofSearch..73/421.5, 28; 179/1002;

[56] References Cited UNITED STATES PATENTS 2,019,541 11/1935 Masten..73/37 3,194,055 7/1965 Knobel .....73/37.5 2,398,958 4/1946 Pellettere..73/37.5 2,078,357 4/1937 Woodmansee et al ..179/100.2 2,548,573 4/1951 Wampole et a1 ..242/75.5 X 2,675,697 4/1954 Quynn et al. 2,722,98811/1955 Hall ..73/28 X 3,138,015 6/1964 Avery ..73/28 X 3,464,257 9/1969Schreiber et 3,475,965 1/ 1969 Koblin et al.

Primary Examiner-Louis R. Prince Assistant Examiner-Daniel M. YasichAtt0meyBamess, Kisselle, Raisch & Choate [57] ABSTRACT A gas samplingdevice having a sampling head with supply and take-up reels mounted onopposite sides of the head to accommodate a filter material in tapeform. The sampling head has two blocks which are yieldably urged towardeach other to clamp a portion of the filter tape between the blocks.Each block is formed with a gas chamber which is positioned so that asample of gas can be passed through the filter tape between the blocks.A spool with cam surfaces having serrated teeth is connected to one ofthe blocks and positioned so that when the spool is rotated the camsurfaces momentarily shift one of the blocks away from the other blockand advance the filter tape through the head. The supply reel isconnected to a drag clutch and the take-up reel is driven through afriction clutch so that the tape is always under a slight tension.

8 Claims, 9 Drawing Figures POWER CYCLK CALIBRATE SHEET 1 [IF 3PATENTEDAPR 11 I972 ATTORNEY5 PATENTEDAPR 11 M2 3,654, 8 O1 IN liN'lURSRICHARD D. lQ EEFER QPHN S. WYMAN,JR.

ATTORNEYS GAS SAMPLING DEVICE This invention relates to gas samplers andmore particularly to a filter tape sampling head and filter tape drivemechanism.

Gas sampling devices usually have a means of passing a predeterminedquantity of the gas to be sampled through a filter membrane. The filtermembrane is then examined to determine what the contaminants were in thesample of gas. For example, the number of particles on the filtermembrane might be counted or a beam of light and a photoelectric cellmight be used to determine the change in translucency ,of the filter andhence the amount of contamination from dust, pollen particles or otherdebris in the gas. The device might also be used to determined theradioactive fallout from nuclear tests or other sources in a gas sample,or a chemically treated filter tape might be used to identify thevarious gases of which a sample is composed. In gas samplers in which afilter material is in the form of a tape it is a problem to properlyload and align the tape in the sampler and to provide a means forpositively and uniformly feeding the filter tape through the samler. pAn object of this invention is to provide a sampling device in which thefilter tape can be readily and easily inserted in and removed from thesampling device.

Another object of this invention is to provide a sampling device inwhich the filter tape is positively and uniformly moved through thesampling device.

Other objects, features and advantages of this invention will beapparent from the following description and drawings which disclose themanner of making, using and carrying out the invention in the best modecontemplated by the inventor.

Drawings accompany this disclosure and the various views thereof may bedescribed as:

FIG. 1, a front elevational view of a gas sampling device illustratingthe sampling head and filter tape mechanism of this invention.

FIG. 2, a view of a portion of a used filter tape with several samplesthereon.

FIG. 3, a front elevational view with broken-out sections of thesampling head of the device of FIG. 1.

FIG. 4, a view on line 4-4 of FIG. 3 showing the arrangement of thelight source, sampling chamber, filter tape, and photoelectric cell.

FIG. 5, a sectional view on line 5-5 of FIG. 3 showing the filter tapeand the manual disengagement cam mechanism.

FIG. 6, a sectional view on line 6-6 of FIG. 3 illustrating the manualdisengagement cam and the filter tape drive spool.

FIG. 7, a view partially in section on line 77 of FIG. 1 il-. lustratingthe take-up spool and take-up clutch assembly.

FIG. 8, a plan view of the gas sampling device of FIG. 1.

FIG. 9, a view partially in section on line 99 of FIG. 1 illustratingthe supply spool and supply clutch assembly.

Referring in detail to the drawings:

FIG. 1 illustrates an air sampling device, designated generally as 20,with a sampling head 22, a filter tape 24, tape supply reel 26, and tapetake-up reel 28 all mounted on a front panel 29. As shown in FIG. 8, avacuum pump 30 driven by a motor 32 is connected to sampling head 22 topull the gas sample through a portion of tape 24. A motor 34 actingthrough a gear train 36, a belt 38 and a clutch assembly 40 takes uptape 24 as it is advanced through sampling head 22, A second clutch 42provides a frictional drag for supply reel 26. A black box 44 cycles andcontrols the various components of sampler 20.

In general, sampling head 22 provides a means for mounting a lightsource and a photoelectric cell to determine the change in translucencyof filter tape 24, a chamber enclosing a portion of tape 24 so that asample of gas can be passed through the tape, and a, means of advancingthe tape through head 22 so that a new portion of the tape can be sealedin the chamber. As shown in FIGS. 3 and 4, sampling head 22 is formedwith a cover 46, a gas inlet block 48, a gas outlet block 50, and a base52. A bore 54 with a countersink 56 at one end and a counterbore 58 atthe other end cooperate with a passageway 60 to form a gas inlet chamber66 in block 48. A connector 62 and a hose 74 provide a means of couplinginlet chamber 66 to the supply of gas to be sampled. A bore 68 withcounterbore 70 at one end and counterbores 72 and 74 at the other endform a gas outlet chamber 76 in block 50. A passageway 78, connector 80,and tube 82 connect outlet chamber 76 to vacuum pump 30 so that a gascan be urged to pass into inlet chamber 66 through filter tape 24 andout through outlet chamber 76 by the action of vacuum pump 30. A lightsocket 84 with bulb 86 extending into bore 54 is mounted in a bore 87and counterbore 89 in cover 46 with an O-ring 88 entrapped betweencountersink 56 and socket 84 to provide an air-tight seal between thelight socket and inlet chamber 66 of block 48. A gasket 90 incounterbore 70 provides a seal between filter tape 24 and chambers 66and 76. A glass plate 92 is sandwiched between two O-rings 94 incounterbore 72 by a retaining ring 96 to seal ofi the lower end of bore68. Retaining ring 96 is seated in counterbore 74 and secured therein byscrews 98. A bore 100, counterbores 102 and 104, and a plate 106fastened in counterbore 104 by screws 108 form a pocket 110 in base 52which captivates a photocell 112 and its socket 114. A spring 115bearing on socket 114 and plate 106 urges photocell 112 into slidingengagement with bore in the upper portion of pocket so that thephotocell bears on retaining ring 96. Ring 96 provides a seal betweenthe exterior of block 50 and photocell 112 so that the light sensitivesurface of the photocell is exposed only to light within chamber 76.Spring 115 urges photocell 112 into contact with outlet block 50 so thatphotocell 104 moves with outlet block 50 when it disengages from filtertape 24. Inlet block 48 and base 52 are rigidly attached to panel 29 byscrews 116 and a spring 118 seated in a pocket in base 52 urges outletblock 50 into engagement with tape 24, thereby clamping and sealing thetape between blocks 48 and 50. Two pins 120 provide alignment guides onwhich outlet block 50 moves when it disengages from tape 24 and inletblock 48.

FIGS. 3, 5 and 6 show the means by which outlet block 50 can be manuallydisengaged from tape 24 and inlet block 48 so that the tape can beinserted into or removed from sampling head 22 and the means by whichblock 50 is automatically momentarily disengaged from inlet block 48 andtape 24 is advanced through the head so that another sample of gas canbe passed through a new portion of filter tape 24. A shaft 121 with aslotted head 122 on one end extends through and is rotatably mounted inoutlet block 50 with a cam 124 connected to the other end so that manualrotation in the clockwise direction (as shown in FIG. 3) forces cam 124into contact with inlet block 48 and disengages outlet block 50 fromtape 24 and inlet block 48 so that the tape can be inserted into andremoved from sampling head 22. A spool 128 with serrated teeth 130 onits edges and two flat sides 132 is connected to a shaft 134 which isrotatably mounted in inlet block 48 and connected to gear train 36.Rotation of spool 128 180 counterclockwise (as shown in FIG. 3) by motor34 causes block 50 to become momentarily disengaged from inlet block 48while teeth I30 dig into tape 24 and advance or move the tape a shortdistance through sampling head 22 and then allow outlet block 50 to movetoward inlet block 48 and reengage tape 24.

As shown in FIGS. 7 and 8, take-up spool 28 is removably connected toslip clutch assembly 40 and is rotated simultaneously with the tapeadvancement spool 128 by motor 34 which is coupled to clutch 40 throughbelt 38. Clutch assembly 40 is formed by a shaft 136 rotatably mountedon 29 by a bushing 138, spacer 140 and a nut 142 threadingly engagingbushing 138. A friction plate 144 is connected to shaft 136 by a setscrew 146 and a pulley 148 is mounted on shaft 136 for rotation withrespect to the shaft. A clutch disc 150 of a material such as cork, isinterposed-between friction plate 144 and pulley 148 to provide afriction clutch. A spring 152 and adjustment nuts 154 threadinglyengaging shaft 136 provide a means of adjusting the pressure with whichpulley 148 bears on clutch disc 150 and plate 144 so that the torquetransmitted from the motor to shaft 136 can be adjusted. Take-up reel 28is formed with an inner plate 156 formed with an inner plate 156 andspacer 158 secured to shaft 136 by pin 160 and an outer plate 162fastened to a hub 164. Hub 164 is removably connected to shaft 136 by aspring-loaded detent ball 166 which extends into a groove 167 in shaft136. A transverse pin 168, captured between hub 164 and plate 162,engages in a slot 170 in the end of shaft 136 so that hub 164 and plate162 will turn with shaft 136. A wear washer 171 is interposed betweenreel spacer 158 and bushing 138.

As shown in FIGS. 8 and 9, supply reel 26 is similar to takeup reel 28and is rotatably mounted on drag clutch assembly 42. Clutch assembly 42is formed by a shaft 172 rotatably and slidably mounted in a bushing 174fastened to panel 29 by a spacer 176 and threaded nut 178. A clutch disc180, of a fraction material such as cork, is interposed between spacer158 of reel 26 and the end surface of bushing 174 and is urged intoengagement with both the bushing and the spacer by a spring 152entrapped between the other end of bushing 174 and threaded adjustingnuts 154. Adjustment of nuts 154 varies the pressure on clutch disc 180and hence the amount of drag or resistance to rotary movement of thesupply reel 26. The drag of clutch assemblies 40 and 42 is adjusted sothat a filter tape inserted in sampling head 22 and coiled on reels 26and 28 is placed under a slight tension and is taken up by reel 28 whenthe tape is advanced by rotary movement of spool 128.

In operating the gas sampler, a coil of unused filter tape is placed onsupply reel 26, shaft 121 is rotated so that cam 124 disengages outletblock 50 from inlet block 48 and the tape is inserted in the resultingslot and connected to take-up reel 28.

' After the tape is inserted in the sampling head, shaft 121 is releasedand spring 118 urges outlet block 50 toward the inlet block 48 and intoengagement with tape 24 so that the tape is clamped or held in a fixedposition in the sampling head between inlet chamber 66 and outletchamber 76. The gasket 90 assures that there is an airtight seal betweenthe chambers and the tape. Black box 44 starts motor 32 and vacuum pump30 draws the gas to be sampled through inlet tube 64 and passageway 60into inlet chamber 66, thence through a portion of the tape and outletchamber 76, passageway 78 and tube 82. Light source 86 and photoelectriccell 112 are energized and monitored by black box 44 to determine thechange in the translucency of the filter tape which is caused by thecontaminants in the gas sample being deposited on the filter tape. Thephotoelectric cell can be monitored either at the end of the samplingperiod to determine the total change in translucency or it can bemonitored throughout the sampling period to provide a continuous sensingof the change in the translucency of the filter tape during the sampleperiod. An adjustable timer in black box 44 provides a predeterminedsampling period and at the end of the sampling period black box 44 shutsoff motor 32 and hence vacuum pump 30 and then it starts motor 34 whichthrough gear train 36 and shaft 134 turns spool 128 180 counterclockwise(as shown in FIG. 3). A snap-action switch which follows a cam withdouble flats on shaft 134 shuts off motor 34 after it has turned spool128 180.As spool 128 is turned 180,teeth 130 simultaneously disengageoutlet block 50 from the tape and engage or dig into the tape andadvance it through the slot in the sampling head. Near the end of the180 revolution of spool 128 teeth 130 disengage from both the tape andoutlet block 50, thereby allowing springs 115 and 118 to urge outletblock 50 toward inlet block 48 and into engagement with tape 24. Whenmotor 34 is started, it simultaneously acts through gear train 36 andbelt 38 to rotate clutch assembly 40 and hence take-up reel 28 so thatused filter tape is coiled into a spool on take-up reel 28 as it isadvanced through sampling head 22 by spool 128. Spool 128 is constructedso that it advances the tape slightly farther than the width of theinlet chamber 66 as shown in FIG. 2 by .the circular deposits ofcontaminants from each sampling period. 7

Sampling head 22 and the tape reel mechanism provide a gas samplingdevice in which the filter tape can be readily and conveniently loadedin the sampling machine and positively advanced through the samplinghead by the spool. The use of tape reels provides a means ofconveniently and economically dispensing the filter material and also asampling machine which can run a large number of individual samples ortests without any assistance by either technical or maintenancepersonnel.

We claim:

1. A sampling device for a filter tape comprising a first block havingan inlet chamber opening to the exterior thereof, a second block havingan outlet chamber opening to the exterior thereof, said openings beingin generally overlying opposed relation to each other, means for guidingthe tape along a path between said blocks and across saidopenings ofsaid blocks, means yieldably urging said blocks into firm engagementwith opposed surfaces of the tape, means for disengaging said blocksfrom firm engagement with the tape comprising a cam carried by one ofsaid blocks and adapted to bear on the other of said blocks such thatmovement of said cam disengages said blocks from firm engagement withthe tape, and engagement means carried by one of said blocks andpositioned in overlying relation with a portion of the tape between saidblocks and adapted to firmly engage and advance the tape across saidopenings when said blocks are disengaged from firm engagement with thetape by said cam.

2. The sampling device of claim I in which said engagement meanscomprises a second cam firmly engaging the tape between said second camand the other of said blocks in advancing the tape across said openings.

3. A sampling device for a filter tape comprising a first block having atape contact surface and an inlet chamber opening to said surfacethereof, a second block having a tape contact surface mating with saidcontact surface of said first block and an outlet chamber with anopening to said contact surface of said second block, said openingsbeing in generally overlying opposed relation, means for guiding thetape along a path between said contact surfaces of said blocks andacross said openings, means yieldably urging said contact surfaces ofsaid blocks into firm engagement with opposed sides of the tape, and aspool mounted for rotation in one of said blocks and positioned inoverlying relation with a portion of the tape and the contact surface ofthe other block, said spool having at least one carn portion engageablewith the tape between said contact surfaces such that rotary movement ofsaid spool including said cam portion disengages said contact surfacesfrom firm engagement with the tape and moves the tape through the blocksbetween said contact surfaces.

4. The sampling device of claim 3 in which at least said one cam portionof said spool has serrated teeth.

5. The sampling device of claim 3 which also comprises a second camcarried by one of said blocks and adapted to bear on the other of saidblocks such that manual manipulation of said cam disengages saidcontacting surfaces of said blocks to facilitate threading of the tapebetween said contact surfaces and across said openings of said blocks.

6. A sampling device for a flter tape comprising a first block having asurface for contacting the tape and a gas sample inlet chamber openingto said surface thereof, a second block having a surface for contactingthe tape mating with said surface of said first block and having a gassample outlet opening to said surface of said second block, saidopenings being in generally overlying opposed relation, means forguiding the filter tape along a path between said surfaces and acrosssaid openings of said blocks, means for incrementally advancing the tapebetween said surfaces and across said openings, a light source carriedby one of said blocks, light from said light source passing through oneof said chambers and the portion of the tape between said openings andinto the other said chambers, a photoelectric cell with itslight-sensitive surface exposed to the light in said other chamber whichpasses through the tape, and means connected to said photoelectric celland adapted to monitor said portion of the tape between said openings toindicate the amount of contaminants deposited on said portion of thefilter tape before said portion of the filter tape is advanced acrosssaid openings of said blocks by said means for incrementally advancingthe tape.

6. The sampling device of claim 6 which also comprises a cam carried byone of said blocks and adapted to bear on the other of said blocks suchthat movement of said cam disengages said surfaces of contact from firmengagement with the tape, and engagement means carried by one of saidblocks in overlying relation with a portion of the tape between saidsurfaces and adapted to firmly engage and advance the tape across saidopenings when said surfaces are disengaged from

1. A sampling device for a filter tape comprising a first block havingan inlet chamber opening to the exterior thereof, a second block havingan outlet chamber opening to the exterior thereof, said openings beingin generally overlying opposed relation to each other, means for guidingthe tape along a path between said blocks and across said openings ofsaid blocks, means yieldably urging said blocks into firm engagementwith opposed surfaces of the tape, means for disengaging said blocksfrom firm engagement with the tape comprising a cam carried by one ofsaid blocks and adapted to bear on the other of said blocks such thatmovement of said cam disengages said blocks from firm engagement withthe tape, and engagement means carried by one of said blocks andpositioned in overlying relation with a portion of the tape between saidblocks and adapted to firmly engage and advance the tape across saidopenings when said blocks are disengaged from firm engagement with thetape by said cam.
 2. The sampling device of claim 1 in which saidengagement means comprises a second cam firmly engaging the tape betweensaid second cam and the other of said blOcks in advancing the tapeacross said openings.
 3. A sampling device for a filter tape comprisinga first block having a tape contact surface and an inlet chamber openingto said surface thereof, a second block having a tape contact surfacemating with said contact surface of said first block and an outletchamber with an opening to said contact surface of said second block,said openings being in generally overlying opposed relation, means forguiding the tape along a path between said contact surfaces of saidblocks and across said openings, means yieldably urging said contactsurfaces of said blocks into firm engagement with opposed sides of thetape, and a spool mounted for rotation in one of said blocks andpositioned in overlying relation with a portion of the tape and thecontact surface of the other block, said spool having at least one camportion engageable with the tape between said contact surfaces such thatrotary movement of said spool including said cam portion disengages saidcontact surfaces from firm engagement with the tape and moves the tapethrough the blocks between said contact surfaces.
 4. The sampling deviceof claim 3 in which at least said one cam portion of said spool hasserrated teeth.
 5. The sampling device of claim 3 which also comprises asecond cam carried by one of said blocks and adapted to bear on theother of said blocks such that manual manipulation of said camdisengages said contacting surfaces of said blocks to facilitatethreading of the tape between said contact surfaces and across saidopenings of said blocks.
 6. A sampling device for a filter tapecomprising a first block having a surface for contacting the tape and agas sample inlet chamber opening to said surface thereof, a second blockhaving a surface for contacting the tape mating with said surface ofsaid first block and having a gas sample outlet opening to said surfaceof said second block, said openings being in generally overlying opposedrelation, means for guiding the filter tape along a path between saidsurfaces and across said openings of said blocks, means forincrementally advancing the tape between said surfaces and across saidopenings, a light source carried by one of said blocks, light from saidlight source passing through one of said chambers and the portion of thetape between said openings and into the other said chambers, aphotoelectric cell with its light-sensitive surface exposed to the lightin said other chamber which passes through the tape, and means connectedto said photoelectric cell and adapted to monitor said portion of thetape between said openings to indicate the amount of contaminantsdeposited on said portion of the filter tape before said portion of thefilter tape is advanced across said openings of said blocks by saidmeans for incrementally advancing the tape.
 6. The sampling device ofclaim 6 which also comprises a cam carried by one of said blocks andadapted to bear on the other of said blocks such that movement of saidcam disengages said surfaces of contact from firm engagement with thetape, and engagement means carried by one of said blocks in overlyingrelation with a portion of the tape between said surfaces and adapted tofirmly engage and advance the tape across said openings when saidsurfaces are disengaged from firm engagement with the tape by said cam.8. The sampling device of claim 6 which also comprises a spool mountedon one of said blocks in overlying relation with a portion of the tapebetween said blocks, said spool having at least one cam portionengageable with a portion of the tape between said surfaces of contactsuch that rotation of said spool including said cam portion disengagessaid surfaces from firm engagement with the tape and advances the tapeacross said openings.